HP LaserJet Pro 400 color Printer M451 series - Manual (Page 175)

4. Remove the jammed sheet by pulling it
straight out.
5. Push the jam-access tray up to close it, and
then replace Tray 2.
NOTE: To close the tray, push in the middle
or with even pressure on both sides. Avoid
pushing on one side only.
Clear jams in Tray 2
1. Open Tray 2.
ENWW Clear jams 157